JPH07100711B2 - Epimerization method of reducing oligosaccharides - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for epimerizing a reducing oligosaccharide.

[Conventional technology]

In recent years, various sugars have been found that show activities such as antibacterial activity and carcinostatic activity, or sugars with other useful applications have been discovered. There is increasing interest as a substance or as a nutritional substance or low calorie sweetener.

In response to this, research on oligosaccharides and application development are activated, and as these demands are cultivated, it is necessary to develop industrial methods for obtaining a wide variety of oligosaccharides, especially oligosaccharides that are rare in nature. Came.

Therefore, the present inventors have conducted various searches for a method of converting an oligosaccharide that is relatively abundant in nature into a rare oligosaccharide, and as a result, have developed a method for industrially advantageously performing an epilation reaction. Came to the idea that was necessary to achieve that end.

Thus, the present invention seeks to obtain the desired valuable epimer of a reducing oligosaccharide by epimerizing C-2 of the reducing terminal aldose residue of the reducing oligosaccharide.

However, regarding the epilation reaction, it is an undeveloped technical field in which reports of oligosaccharides are hardly found, regardless of conventional monosaccharides, and slightly,
A method that uses the so-called Lobry de Bruyn transition via 1,2-enediol in an aqueous solution weakly alkaline with ammonia, which is known as a classical epimerization method for monosaccharides,
Bi epimerizing melibiose with bismuth and molybdic acid
The current situation was that lik's method [see LISTY.CUKROVARNICKE 94/1978 P88] was only known.

[Problems to be solved by the invention]

Moreover, the first method to utilize the Lobry de Bruyn transition is
In addition to the extremely slow reaction, there are many side reactions, and a large amount of by-products are mixed in, which cannot be an industrial method. Since the temperature is as high as 90 ° C., the reaction time is too long for 6 hours, and the epilation rate is only 20%, it is necessary to further improve it as an industrial method.

In view of such circumstances, the present inventor has earnestly studied an oligosaccharide epimerization method using a molybdic acid-based catalyst having a high epilation rate and a high sugar recovery rate, and as a result, excellent reaction results can be obtained under specific conditions. And has reached the present invention.

[Means for solving problems]

That is, the present invention is a method for epimerizing a reducing oligosaccharide characterized in that a reducing oligosaccharide-containing solution is reacted in the presence of molybdic acid or a salt thereof at pH 2.5 to 4 and a reaction temperature of 90 to 140 ° C. is there.

The present invention will be described in detail below.

The starting oligosaccharide used in the present invention is preferably a reducing oligosaccharide.

Specific examples of this reducing oligosaccharide include melibiose,
And gentio-oligosaccharides (eg, gentiobiose, gentiotriose, gentiotetraose, gentiopentaose, gentiohexaose), and isomaltooligosaccharides (eg, isomaltose, isomaltotriose, isomalttetraose, isomaltopenose) , Isomalt hexaose), and maltose, and laminari oligosaccharides (eg, laminaribiose, laminaritriose, laminaritetraose, laminaripentaose, laminarihexaose, laminariheptaose)
Etc. can be given.

These oligosaccharides are C-2 of the aldose residue at the reducing end.
Is converted into an epimer and converted into each epimer.

Molybdic acid or its salt is used as a catalyst for the epitaxy method of the present invention.

Examples of molybdates include ammonium molybdate, potassium molybdate, sodium molybdate,
Examples thereof include calcium molybdate and acetylacetone molybdate.

These can also be used after being dissolved in the following solvents or immobilized as molybdate ions on ion exchange resins, ion exchange fibers and the like.

The amount of these catalysts used is 0.1 to 1.5% by weight based on the raw sugar.
And 0.2 to 1.0% by weight is particularly preferable. If the amount of the catalyst is out of this range, the amount of the catalyst is too small, and the reaction rate becomes too slow.

Examples of the solvent used in the reaction include water or alcohols such as methanol and ethanol, n-propanol, isopropanol, n-butanol, isobutanol, acetone, dioxane, DMF, DMSO and the like, and a mixed solvent thereof.

The pH of the reaction solution is preferably in the range of 2.5-4. This makes the pH
When the value is low, hydrolysis of oligosaccharides proceeds, and when the value is too high, the epilation rate decreases.

The reaction temperature is 90 to 140 ° C, preferably 110 to 130 ° C. If the temperature exceeds 140 ° C and the temperature becomes too high, a side reaction occurs and the reaction solution is browned to lower the yield. Also, 90 ℃
If it is too low, the reaction rate is slow and the epilation rate is lowered, which is not preferable.

Although the reaction time is one of the features of the method of the present invention, the Bi
It takes less time than the lik method.

However, if the reaction time is too short, the reaction does not reach equilibrium, which is not preferable. Therefore, it is better to carry out the reaction for at least 5 minutes. When the reaction is carried out at the above preferable reaction temperature, the reaction time is 10 to 40.
Good results can be obtained in minutes. In addition, although better results can be obtained by stirring during the reaction, this is not essential.

In order to carry out the method of the present invention, molybdate and water, a solvent such as alcohol and a reducing oligosaccharide are put in a reactor,
After adjusting the pH with an acid or the like, the mixture is heated with stirring to carry out the epilation reaction.

The epimer can be removed after the epilation reaction by a known separation method, that is, by passing the reaction solution through a column of a cation exchanger loaded with a metal selected from calcium, barium, strontium, aluminum and the like. .

〔Example〕

 The present invention will be described below with reference to examples.

In addition, high-performance liquid chromatography (hereinafter referred to as HP
LC), but specifically, a post-column detection method using 2-cyanoacetamide as a color reagent (for details, see
S.Honda et al. Anal. Chem. 52.1079 (1982)) using a fluorescence detector.

Example 1 54 g of melibiose, 108 mg of ammonium mobridenate and 36 g of water were placed in an autoclave and pH was adjusted with 2N sulfuric acid.
After adjusting to 3.0, the mixture was heated and reacted at 120 ° C. for 30 minutes with stirring.

Immediately after the reaction, the reaction solution is cooled and the cation exchange resin Dowe
The catalyst was removed by passing through x50W-X2 and anion exchange resin Dowex MSA-1.

As a result of analyzing the sugar in the obtained liquid by HPLC, it was confirmed that 36% of the melibiose initially added was converted to an epimer.

In addition, the other components are 62% melibiose and mannose.
It was 0.3%, glucose 0.7%, and galactose 1%.
The sugar recovery rate (yield) relative to the raw sugar was as high as 98%.

Examples 2 to 12 As shown in Table 1, various raw sugars, reaction conditions, catalysts, raw material charges, and solvents were combined, and the same procedure as in Example 1 was carried out. The results are shown in Table-1.

[Effect of the Invention] The present invention is an epimerization method for reducing oligosaccharides, which has a shorter reaction time than conventional methods, a high epilation rate, and excellent selectivity.

Thus, the present invention enables an industrial process for producing a valuable epimer of an oligosaccharide, which is considered to be more important in the future, and is expected to further expand its use.

Claims (3)

[Claims] 1. A method for epimerizing a reducing oligosaccharide, which comprises reacting a solution containing a reducing oligosaccharide in the presence of molybdic acid or a salt thereof at a pH of 2.5 to 4 and a reaction temperature of 90 to 140 ° C. . 2. The reducing oligosaccharide according to claim 1, wherein the raw material reducing oligosaccharide is selected from melibiose, gentiooligosaccharide, isomaltooligosaccharide, maltose and laminari oligosaccharide. Epi method. 3. The method for epimerizing a reducing oligosaccharide according to claim 1, wherein the reaction is carried out for 5 minutes or more.